This invention pertains to sanding boards for supporting an abrasive material, and more particularly to a sanding board having a flexible base for supporting the abrasive material, and wherein the flexible base can be configured in a contoured shape and held in the contoured shape.
The process of xe2x80x9csandingxe2x80x9d entails using an abrasive material which is adhered to a first surface to remove matter from a second surface. For example, the sanding process can be used to remove paint and other applied coatings from an object so that the object can be repainted or refinished. In other applications the sanding process can be used to remove matter from an object to shape the object into a final shape. For example, in automotive body work a weld seam between two body panels can be smoothed to give the final painted panels an integral appearance. Typically, the sanding process is performed with a sanding board or a sanding block which supports a sheet of abrasive material, such as sandpaper.
Many times the surface to be sanded is a contoured surface, and not a flat surface. However, most apparatus for performing the sanding process comprise an essentially flat base for supporting the abrasive material. When sanding a contoured surface with a flat sanding board it can be difficult to assure even coverage and produce a finished surface which does not have flat spots as a result of being sanded with the flat sanding board. Further, since only a small portion of the flat board contacts an equally small portion on a contoured surface which is being sanded, the sanding process can take a considerable period of time to complete. Accordingly, what is needed is a sanding board which can accommodate contoured surfaces to produce a smooth finished surface and which reduces the time required to perform the sanding process.
A number of prior art devices have attempted to address this problem. U.S. Pat. No. 470,794 to Shempp employs a series of stacked plates which can be moved relative to one another to attempt to match the contour of the surface being sanded. However, this device limits the contour-matching abilities of the sanding board to the thickness of the plates being used, and so a series of high point lines can result where the edges of the plates meet. U.S. Pat. No. 1,570,177 to Pointer uses a similar assembly of a plurality of plates, and therefore suffers from the same limitations as does the Shempp patent.
U.S. Pat. No. 3,1 23,947 to Rawley discloses a contourable sanding board having a flexible base, a front and a rear frame member attached respectively to the front and rear of the flexible base, and a central frame member connected to the center of the flexible base. A first turnbuckle connects the front frame member and the central frame member, and a second turnbuckle connects the rear frame member and the central frame member. By adjusting the turnbuckles the front and rear frame members can be pulled towards, or pushed away from, the central frame member. By pulling one of the end frame members towards the central frame member, the flexible base is caused to curve in a convex shape between the end and the central frame member; by pushing one of the end frame members away from the central frame member, the flexible base is caused to curve in a concave shape between the end and the central frame member.
U.S. Pat. No. 4,944,128 to Reiter attempts to address the problem by using a relatively thin, flexible sanding board to which sand paper can be attached. A secondary plate is attached to the sanding board at each end of the sanding board. Moveable wedge members are disposed between the sanding board and the secondary plate which, when moved in one direction or another, effectively shorten or lengthen the length of the secondary member with respect to the sanding board, thus pulling the sanding board into either a convex or a concave shape.
U.S. Pat. No. 5,203,123 to Travis provides for a flexible sanding board which uses a flexible main body impregnated with metal rods. The flexible body can be bent to a desired contoured shape, and will be held in this shape by the metal rods. However, if significant forces are applied to the flexible body during the sanding process, then the metal rods can be bent out of the desired shape.
U.S. Pat. No. 5,700,187 to Balbi discloses a sanding board which can be contoured to conform to a surface to be sanded. The sanding board comprises a flexible base for supporting a sheet of sanding material. Each end of the flexible base is attached to a cross journal which is configured to receive knobs having a threaded portion. A frame or guide fits over the journals, and incorporates two slots which receive the threaded portion of the knobs. Thus, the knobs can be used to tighten the frame against the journals. By moving the knobs in the slots, the journals are either pushed apart or pulled together, which has the effect of respectively pushing apart the ends of the flexible base or pulling the ends towards one another. When the ends are pushed apart, the sanding base is forced into a concave form; when the ends are pulled together, the based is forced into a convex form.
One common aspect of most of the prior art devices is that they produce a symmetrical curve, or two symmetrical curves. That is, the first half of the sanding board, when curved, produces a curve which is identical, but mirrored, as the curve in the second half of the sanding board. It is desirable to be able to configure the base of the sanding board with an asymmetrical curve since frequently surfaces such as boat hulls and automobile bodies have progressively curves surfaces. While some of the prior art devices (for example, the devices described by Rawley and Balbi) can be configured with an asymmetrical curve, this requires separate adjustment of each of the two adjustment points.
The present invention includes an apparatus for supporting an abrasive material, such as sandpaper, and allows the base which supports the abrasive material to be variably contoured to conform more nearly to a surface intended for finishing by the abrasive material.
In its most general form the invention includes a flexible base defined by a first end and a second end. The flexible base is further defined by a lower surface configured to support the abrasive material and an upper surface opposite the lower surface. The flexible base is fabricated from a resilient material so as to assume an essentially flat shape when the ends of the flexible base are not acted on by external forces. The apparatus further includes a front frame member attached to the flexible base proximate the first end, and a rear frame member attached to the flexible base proximate the second end. The apparatus has an adjustable connecting link having a first end and a second end. The first end of the adjustable link is connected to the front frame member in relatively fixed relation thereto. The second end of the adjustable link is connected to the rear frame member by a variably positionable connection.
In a first embodiment of the present invention the rear frame member of the apparatus defines a hole there through for receiving the second end of the adjustable connecting link. The hole is defined by a first side which faces in a general direction towards the front frame member, and a second side which faces in a general direction way from the front frame member. The first end of the adjustable connecting link comprises a threaded rod which is connected to the rear frame member in a variably positionable manner by a first nut and a second nut threadably mounted on the threaded rod. The first nut is adjacent the first side of the hole, and the second nut is adjacent the second side of the hole. By moving the first and second nuts in conjunction in a direction away from the front frame member, the frame members are pushed apart, forcing the flexible base into a concave position. Likewise, by moving the first and second nuts in conjunction in a direction towards the front frame member, the frame members are pulled together, forcing the flexible base into a convex position. The flexible base is held in the contoured position by the nuts on the threaded rod.
In a second embodiment of the apparatus the rear frame member defines a hole there through for receiving the second end of the adjustable connecting link. The hole is defined by a first side which faces in a general direction towards the front frame member, and a second side which faces in a general direction way from the front frame member. The second end of the adjustable comprises a rod disposed through the hole. The apparatus further comprises a release device hingedly attached to the rear frame member and facing the second side of the hole in the rear frame member. The release device has an opening disposed therein, and the rod is disposed through the opening. A spring is disposed between the rear frame member and the release device to bias the release device against the rod to arrest movement of the rod in the hole. By pushing the release device towards the second side of the hole in the rear frame member the rod is allowed to move in the hole. The front and rear frame members can then be pushed apart or drawn together to cause the flexible base to curve in a respective concave or convex shape. When the release device is released the spring biases the device into the rod, holding the rod and thus the flexible base in fixed position.
In a third embodiment of the present invention the adjustable connecting link is connected to the rear frame member in a variably positionable manner by an intermediate link. The intermediate link has a first end and a second end. The first end of the intermediate link is pivotally connected to the rear frame member, and the second end of the connecting link is pivotally connected to the intermediate link at a point distal from the first end of the intermediate link. Preferably, the point where the intermediate link is connected to the rear frame member and the point where the intermediate link is connected to the connecting link are located along an axis which is variably about 40 degrees from either side of normal to the upper surface of the flexible base. Also preferably the apparatus includes a lock device configured to fixedly secure at least one of the pivotable connection points of the intermediate link to thereby prevent rotation thereof. The locking device can be released to allow the connection point to rotate. When the locking device is released the connection point between the intermediate link and the adjustable link can be moved towards the front frame member to effectively lengthen the distance of the adjustable link and thus push the front and rear frame members apart. This in turn causes the flexible base to curve in a concave shape. The base can be held in this shape by locking the locking device. Likewise, when the locking device is released the connection point between the intermediate link and the adjustable link can be moved towards the rear frame member to effectively shorten the distance of the adjustable link and thus pull the front and rear frame members together. This in turn causes the flexible base to curve in a convex shape.
These and other aspects of the present invention will now be described in fuller detail.